Characterization of Partial Resistance to Bean Rust Disease caused by Uromyces appendiculatus in Seven Common bean Varieties

Partial resistance (PR) to bean rust (Uromyces appendiculatus) in seven bean varieties was determined through three epidemiological parameters, final rust severity (FRS %), area under disease progress curve (AUDPC) and rate of disease increase (r-value) at adult plant stage under natural infection in open field, and four components of resistance (incubation period, latent periods, infection frequency and Pustule size under artificial inoculation in greenhouse) at seedling stage under artificial inoculation in greenhouse. Resistance parameters under both field and greenhouse conditions were varied significantly among bean varieties tested in different years. Montcalm, Nebraska and Bronco were classified partially resistant varieties with decreasing the amount of rust infection and disease development, whereas Karnak, Giza 6, Paulista and Contender were exhibited fast-rusting varieties based on both open field and greenhouse experiments. The partially resistant varieties had higher amounts of three enzymes catalase (CAT), peroxidase (POX) and polyphenoloxidase (PPO) compared with fast-rusting varieties. High significant correlations (r2) were observed among resistance parameters in both field and greenhouse experiments. Correlation matrix suggests that AUDPC and LP50 were good and more reliable parameters for evaluation and selection for resistance to bean rust.